Process for abrasion resistant cellulose products



Sept. 15, 1970 A.- E. LAUCHENAUER 8,

PROCESS FOR ABRASION RESISTANT GELLULQSE PRODUCTS Fil ed May 5, 1966 2 Sheets-Sheet 1 FIGB. FIG.4.

INVENTORZ ALFRED E. LAUCHENAUER ATTYS.

M m A. E. LAUCHENAUER 3,528,72

PROCESS FOR ABRASION RESISTANT CELLULOSE PRODUCTS Filed May 5, i966 2 Sheets-Sheet 2 mvEN'roR: ALFRED E. LAUCHENAUERI 3,528,762 PROCESS FOR ABRASION RESISTANT CELLULOSE PRODUCTS Alfred E. Lauchenauer, Horn Thurgau, Switzerland, as-

signor to Raduner & C0. A.G., Horn, Switzerland, a corporation of Switzerland Filed May 3, 1966, Ser. No. 554,926 Claims priority, application Switzerland, May 10, 1965, 7,718/65; Austria, Jan. 21, 1966, A 577/66 Int. Cl. D06m 1/00, 13/12 US. Cl. 8-116 7 Claims ABSTRACT OF THE DISCLOSURE Cellulosic fibers, impregnated with a finishing agent capable of cross-linking cellulosic hydroxyl groups and a catalyst for the cross-linking reaction, and containing not more than about 30%, by weight, of moisture, are subjected to an atmosphere of a gaseous agent which interferes with cross-linking under such conditions as to interfere with cross-linking essentiallyat the surface periphery of the cellulosic fibers. The fibers are then subjected to conditions causing cross-linking of the cellulosic hydroxyl groups by the finishing agent so that the degree of crosslinking is greater in the core of the fibers than at the surface periphery.

The present invention relates to wrinkle and crease resistant cellulosic materials having improved abrasion resistance and to a process for their production. More particularly this invention relates to improved cellulosic textile materials and a process for producing these materials whereby they exhibit a greater degree of intermolecular cohesion in the interior of the cellulosic fibers than at the peripheral portions of these fibers.

High-grade finishing techniques which, by increasing intermolecular cohesion, particularly by crosslinking, give fabrics containing cellulosic fibers such features as crease recovery in the dry and/ or Wet state, non-ironing properties, dimensional stability, wash-resistant creases, permanent finishes, and special effects such as fiameproof and soil-repelling qualities, apart from causing a decrease in tensile strength and a deterioration in resistance to tearing and tear propagation, have the serious disadvantage of reducing the abrasion resistance.

Attempts have been made to avoid loss of abrasion resistance by adding softeners and other agents, by using special combinations of finishing agents, or by varying the reaction conditions during crosslinking, but in practice these. methods either gave no noticeable improvement in the wear resistance of the material or had such a bad effect on other desirable properties that the required finish was lost or failed to materialize.

Techniques, such as disclosed by A. S. Cooper, et al. in 54 American Dyestulf Reporter, pp. 89-94 (Sept. 13, 1965) and by Gagarine et al. in French Pat. 1,343,029 issued Oct. 7, 1963, having been proposed for crosslinking cellulosic fibers by applying resins to fabrics by either back coating or face coating. These processes produce fabrics having one side completely uncrosslinked.

Also due to the fact that yarns are intersected and crimped, segmented crosslinking effects are obtained. This can easily be demonstrated by staining techniques. Such prior art crosslinking techniques resulting in segmented crosslinking were proposed under the assumption that abrasion strength losses due to crosslinking could be reduced by having crosslinked segments alternating with uncrosslinked segments along the axis of fibers and yarns.

Such techniques are unsatisfactory and unreliable. Initially it is extremely difficult to control the depth of penetration of the catalyst, the catalyst deactivator, or even United States Patent ice the crosslinking agent. Thus results cannot be duplicated. These processes leave the entire front or back of a given fabric uncrosslinked depending on the method and/or side of application. Segmentation exists along both individual fibers and yarns even within treated areas. This has been found to be true even if both the front and back of a fabric are treated in accordance wth these prior art methods.

Moreover such face or back coating techniques necessitate the use of very heavily thickened solutions to control the penetration of the coating paste, i.e., thickeners in relatively high concentrations have to be used, which shOW undesirable side-effects, in particular serious stiffening and an undesirable harsh hand.

It is an object of this invention to provide fabrics containing cellulosic materials which in addition to exhibiting good wash and wear, permanent press, wrinkle resistant, and crease retention characteristics also exhibit good abrasion resistance characteristics.

Another object of this invention is to provide a cellulosic fibers which is impregnated with a compound capable of forming intermolecular bonds between cellulosic hydroxy groups wherein said fiber exhibits a substantially uniformly higher degree of intermolecular bonding between said cellulosic hydroxy groups in the interior regions of the diameter of the fiber throughout the length of the impregnated fiber than is exhibited at the periph eral portions of the fiber.

A further object is to provide a process for the production of such fabrics characterized by a uniform higher degree of cellulosic intermolecular cohesion in the interior regions of the diameter of each individual cellulosic fiber throughout the length of the fiber than is exhibited at or near the surface periphery of the fiber.

Other objects will become readily apparent to those skilled in the art from the following description and claims.

It has now been found that high-grade finishing eifects based on an increase in the intermolecular cohesion of the cellulosic materials can be obtained together with improved surface properties, particularly improved mechanical properties such as improved abrasion resistance, by applying a finishing agent capable of forming intermolecular bonds between cellulosic hydroxyl groups to a fabric composed at least in part of cellulosic fibers and maintaining said finishing agent in contact with said fabric in the presence of hydroxyl groups, finishing agents and reaction catalysts while in effect varying ratio of hydroxyl groups, finishing agents and catalysts present on the peripheral portions of the cellulosic fibers at a time before final reaction of the finishing agent with the fabric whereby said fibers exhibit a substantially uniformly lower degree of intermolecular cohesion between said cellulosic hydroxyl groups at and near the surface periphery of the fiber throughout the length of the fiber than is exhibited in the interior regions of the diameter of the fiber.

According to this process a wrinkle and crease resistant, fabric containing cellulosic material is provided having improved abrasion resistance which. comprises yarns containing cellulosic fibers impregnated with a compound capable of forming inermolecular bonds between cellulose hydroxyl groups wherein said fibers exhibit a substantially uniformly lower degree of intermolecular cohesion between said cellulosic hydroxyl groups at and near the surface periphery of the fiber than is exhibited in the interior regions of the diameter of the fiber throughout the length of the impregnated fiber. There is a decrease in the degree of intermolecular bonding or crosslinking going outward from the central core of each individual fiber to the surface periphery of that fiber. The distinction cannot be quantitatively expressed in an exact manner. However, it can be shown clearly in a qualitative manner by microphotography of dye stained fibers. By this method heavily crosslinked areas of the fibers can be isually differentiated from less heavily or uncrosslinked areas of the fibers. The dyestuffs utilized penetrate into and dye uncrosslinked parts of the fibers.

By segmentation is meant that there are areas in individual fibers or threads which do not present this substantially uniform increase of internal intermolecular cohesion over the length of fibers and yarns. That is within a treated fabric area there will be areas of strong crosslinking adjacent to relatively or completely uncrosslinked areas either along the length of the yarn or fiber or a distinct asymmetrical distribution of crosslinks will be noted across the diameter of certain parts of a significant number of yarns or fibers.

The accompanying figures are diagrammatic illustrations presented to facilitate an understanding of the invention.

FIG. 1 is a representation of a lengthwise view of cellulose yarns treated in accordance with the process disclosed in the cited American Dyestutf Reporter reference or the French patent. Dark areas indicate uncrosslinked areas while light areas indicate heavily crosslinked areas. Resin concentration has been increased from right to left. This is an excellent example of segmentation along the length of a fabric yarn.

FIG. 2 shows a similar representation of cellulose yarns treated in accordance with the instant process with resin concentration increasing from left to right. This shows individually uniform cross-linking over the entire length for each yarn.

FIG. 3 is a representation of a view of cellulose yarns treated in accordance with the abovementioned prior art disclosure. This is an excellent example of segmentation across the diameter of the yarn, i.e., from the interior core out to the outer peripheral area.

FIG. 4 is similar to FIG. 3 except that it depicts yarns treated with a lower concentration of crosslinking resin.

FIG. 5 is similar to FIG. 3 except that it depicts yarns treated in accordance with the instant process. Substantially no segmentation is present.

FIG. 6 is similar to FIG. 3 except that it depicts yarns treated with a higher concentration of crosslinking resin. This shows what is probably the most detrimental segmentation of both types.

FIG. 7 is a representation of a cross-sectional view of individual fibers in a cellulose yarn. Cross-sectional views of this type are prepared by dyeing the treated yarn, polymerizing the yarn in situ and then cutting the yarn across its length at as close to a 90 angle as is possible.

Dyestuffs such as Chlorantinlichtblau 2 BLL (Color Index: Direct Blue 80) produced by Ciba, Ltd. can be used to determine the differences in the degree of intermolecular cohesion. For example, the fabric can be tested by taking and contacting a sample of 30 grams weight for about 30 minutes at 80 C. with a solution containing about 0.5 gram per liter of dyestuff and about 10- grams per liter of sodium sulfate followed by a hot and cold rinse and then drying it to obtain the discussed results.

For the purposes of this invention the term yarns is used interchangeably with threads throughout this specification. Yarns are to be regarded as twisted groups of fiber 'which themselves may be staple cotton or cellulosic fibers or continuous filaments.

The term while in effect varying the ratio of hydroxyl groups, finishing agents and catalysts means that the molecular ratio of the three relative components, i.e., (1) available hydroxyl group; (2) finishing agent; and (3) catalyst, is varied in such a manner that the ratio of hydroxyl groups to either finishing agent or effective catalyst is greater at the surface of the fibers than in the interior. By creating this ratio more intermolecular cohesion occurs in the interior of the individual fibers and threads than toward their surface periphery because more chemical reactions will take place between cellulosic hydroxyl groups and finishing agents in the interior than at the exterior of the individual fibers or threads as will be explained hereinafter. The total number of available hydroxyl groups includes cellulosic hydroxyl groups and any added hydroxyl groups present in the form of distillable hydroxyl compounds.

Due to the versatility of the instant process it is feasible, by proper selection of treating conditions, to obtain yarn core crosslinking in addition to fiber core crosslinking. In yarn core crosslinking the median degree of crosslinking of individual cellulose fibers increases from the periphery to the core of the yarn. This phenomenon is shown in FIG. 8, which is a representation of a cross-sectional view of a cellulose yarn. Both the single fibers lying near the surface of the yarn (FIG. 8c) and those located near the center of the yarn (FIG. 8d) exhibit fiber core crosslinking, the former having, however, a wide peripheral, ring-like area of cellulose which is only feebly crosslinked or not crosslinked at all (FIG. 8a). These areas on the exterior fibers enclose cores having higher degrees of crosslinking (FIG. 8b) than the fiber cores situated near the center of the yarn.

Utilizing the processes described hereinafter one may, for instance, obtain a material in which the median degree of crosslinking of single fibers in a yarn is virtually the same with possibly some minor deviation over the whole cross-section of yarns, i.e., the large majority of the single fibers are core-crosslinked to the same degree. By varying processing conditions one may produce fiber core and yarn core crosslinking at the same time, i.e., there is an approximately equal decrease of the median degree of crosslinking from the periphery of both the yarn and its single fibers to the central part of the yarn and its individual fibers. In addition one may also vary, again by selecting proper processing conditions, the difference between the degree of crosslinking of the peripheral parts and the core of individual fibers, in particular the thickness of the ringlike peripheral areas showing no or only feeble crosslinking.

Varying the molar ratio of the three interacting components, namely: (a) the hydroxyl groups available for bridge-building, (b) the finishing agent for improving the intermolecular cohesion of the cellulose, and (c) the effective amount of catalyst, at the earliest immediately :upon application, or at the latest before the washproof fixation of the finishing agent, so that the ratio of the number of hydroxyl groups available for bridge building with the finishing agent to the the effective concentration of at least one of the other two components is greater at the surface of the fibers and/ or threads than in the interior of the fibers and/ or threads, whereupon the finishing agent is fixed in the material washproof fashion, preferably by heat treatment, improves the intermolecular cohesion of the cellulose. This results in a good finish with considerable improvement in surface properties, in particular better abrasion resistance and a better hand.

The ratio of the number of hydroxyl groups available for bridge-building with the finishing agent to the number of molecules of finishing agent and/or the effective concentration of the bridging catalyst at the surface of the fibers or threads can be increased in the period between the application of the finishing agent and its fixation in the following Ways:

(I) Surface deactivation.This is achieved by reducing the effective amount of catalyst at the surface of the fibers and/or threads, (eg. by at least partial superfical neutralization of the catalyst). This creates a situation where more reactions creating intermolecular bonding will occur in the interior portions of the fibers and/or threads because surface deactivation of the catalyst reduces the amount of catalyst available to catalyze reactions at the exterior portions of the fibers and/or threads.

In the case of acid catalysts, for example, the effective amount of catalyst can be reduced by surface treatment with alkaline or buffering agents (anti-catalysts). The reduction in the effective amount of catalyst at the surface may take place before or after evaporation of the liquid phase in which the finishing agent and/or catalyst is applied to the material (e.g. water). The deactivating agents can be applied in the form of a solution, a dispersion or emulsion, or a gas. If a liquid preparation is used, the liquid phase may or may not be miscible with the solvent used in applying the finishing agent and the catalyst. Where necessary, it may be used in a more or less thickened, preferably highly thixotropic form, or in the form of a foam. The agents used for the surface deactivation of the catalyst may be simple alkaline or buffering agents or may be so chosen that, owing to the structure of their molecule (arrangement of polar groups), the shape of their molecule, or their molecular weight, they have either no or at most a limited ability to diffuse into the fibers or threads, which effectively confines their activity to the surface. The catalyst can also be dissolved off the surface, where necessary with a solvent that is immiscible or only slightly miscible with that still on the fiber or thread or in which only the catalyst, and not the finishing agent, dissolves easily. Salts or other compounds may be added to adjust the dissolving power of the solvent.

Anticatalysts which can be used for acidic catalysts include any substance which reduces the acidic properties by neutralization, buffering action, insolubilization. Examples of neutralizing anticatalysts are soda ash, ammonia, amines, etc., such as octadecyl amine and morpholine. Examples of buffering anticatalysts are buffering systems such as ammonia salts, generally salts of weak acids and strong bases. In the case of metal salt catalysts either the cation or the anion of the catalyst molecule could be rendered inactive by the formation of an insoluble salt.

Anticatalysts for alkaline catalysts include neutralizing anticatalysts such as acidic substances in gaseous or liquid form, for example, sulphur dioxide, solutions of weak or strong organic or inorganic acids, and buffering anticatalysts such as buffering systems consisting of salts of strong acids and weak bases. As mentioned above inactivation can also be achieved by the formation of an insoluble salt. Anticatalysts, particularly if applied in the form of solutions or dispersions, with large or polar molecules have advantages due to the slower and shallower penetration of such compounds. Octadecyl amine is an example of a polar, rather large, molecule with anticatalyst properties.

The deactivating treatment may be carried out at room temperature or at elevated temperatures.

In certain circumstances, the anti-catalysts can 'be applied to the material together with the finishing agent and catalyst. Subsequently they can be made to migrate to the surface of the fibers or threads, e.g., by evaporating the liquid phase, whereupon they reduce the effective concentration of the catalyst at the surface.

A particularly simple embodiment of this idea consists in subjecting the celluosic fibers and threads to the action of gaseous agents capable of deactivating the catalyst by buffering and/ or chemical reaction. These agents are introduced at some time between the application of the finishing agent and its final fixation, preferably during the drying process (evaporation of the liquid phase, e.g., Water, in which the finishing agent is applied) or during the washproof fixation of the finishing agent in the cellulose. For example, a preferably low concentration of these gaseous agents can be maintained in the chambers used for drying and/or washp'roof fixation.

In the case of acidic reaction catalysts one may for instance use ammonia gas as the deactivating agent prior to or during drying (evaporating the solvent from which the finishing agent has been applied), preferably between drying and the washfast fixation or during the washfast fixation of the crosslinking agent. It has been found that the reaction time may be varied within wide limits, i.e., one may effect deactivation in a very short time or one may extend the deactivating time and carry out the Whole treatment aiming at washfast fixation of the crosslinking agent in presence of a gaseous anticatalyst. Not only deactivating times, but also the concentration of the deactivating agent may be varied within wide limits. It is preferred to keep them very low, which of course is ad vantageous in mill production. Generally speaking the concentrations of gaseous anticatalysts are between 5 to 4000 millimols, usually between 5 to 600 millimols, per cubic meter, and in the range of 1:500 to :1 with respect to the concentration of the reaction catalyst to be deactivated which is present in the textile material.

If short deactivating times are used it may be advantageous to circulate gaseous anticatalysts inside the re action chamber to obtain uniform interaction with the reaction catalyst.

Deactivation may be effected immediately before the crosslinking agent is rendered fast to Washing (e.g., by a heat treatment) when low concentrations of the gaseous anticatalysts and very short reaction times are used.

(II) Surface solubilization of finishing agent or catalyst.By reducing the concentration of finishing agent at the surface of the fibers or threads a situation is created whereby there is a greater ratio of cellulosic hydroxyl groups to finishing agent at the surface than in the interior since the concentration of finishing agent has been removed at the surface but not toward the interior.

This may take place before, during or after the evaporation of the liquid phase used in applying the finishing agent and the catalyst, and preferably by surface dissolving, possibly with the same solvent. as that used in treating the material or else with another solvent which may not be completely miscible with that in the fiber or thread, but in which the finishing agent dissolves easily. Salts or other substances may be added to the solvents to adjust their dissolving power.

(II) Addition of distillable hydroxyl compounds. The desired effect is achieved by increasing the total number of hydroxyl groups capable of forming bridges with the finishing agent at the surface of the fibers or threads. The extra hydroxyl groups at the surface compete with the cellulose hydroxyls during bridge-building and thus reduce the number of reactions between cellulosic hydroxyl groups and finishing agent at the surface of the fibers or threads in relation to the number of such reactions taking place in the interior of the fibers or threads. Distillable hydroxyl compounds can be applied together with the finishing agent and/or catalyst, their boiling point being so chosen that upon evaporation of the liquid phase (generally water) they vaporize only at the end of the drying process or preferably during the subsequent heat treatment and thus accumulate on the surface of the fibers or threads. The hydroxy compounds can also be applied afterwards, and again it is possible to use compounds whose molecular structure, shape or weight is such that their ability to penetrate into the fibers or threads is reduced to a minimum. Application may be from solution, dispersion, emulsion or the gas phase, and in the case of application in the liquid phase in highly thixotropic or foam form.

The humidity content of the textile material and the gas atmosphere duirng deactivation may be used to vary effects in particular when utilizing gaseous deactivating agent. If yarns in the textile material contain water which is only mechanically bonded to the cellulosic material (when, for instance, the wtaer content is higher than 30%), the yarn-core crosslinking may be achieved. The single fibers still showing fiber-core crosslinking in most cases. If, however, deactivation takes place in presence of only small amounts of water or at a low degree of air humidity, then only fiber-core crosslinking is obtained,

i.e., the fibers show substantially the same median degree of crosslinking irrespective of their location in the yarn. In the preferred embodiments of the invention the cellulosic fibers present in the textile material contain not more than 30%, and preferably less than 20% water when deactivation starts, and the water content of the gas atmosphere containing the gaseous deactivating agent contains usually to 15 g. water per one cubic meter of air. (These ranges are based on a temperature of 20 C.)

To obtain comparable effects under different conditions, the gas atmosphere should contain more water when less humidity is present inside the cellulosic fibers. -If the fibers are substantially dry and reaction times short it may be necessary to raise the humidity of the gas atmosphere to near the point of saturation. If on the other hand the fibers are wet, no or little humidity has to be introduced into the gas atmosphere containing the deactivating gas.

A combination of all the above described methods may be utilized to create the same effect, i.e., reduce the number of reactions between cellulosic hydroxyl groups and finishing agents at the surface of the fibers or threads in relation to the number of such reactions taking place in the interior of the fibers or threads. The effect may be achieved by repeating, varying or applying the above methods in various steps.

A special embodiment of this invention consists in providing that the solvent for the agents to be applied to the material or dissolved from its surface be a compound with a swelling effect on cellulose. Alternatively, such compounds can be applied at a later stage (but before the increase in the intermolecular cohesion of the cellulose). These non-aqueous swelling agents when used in this manner must have a boiling point at the most about 50 C. below or about 70 C. above the temperature used for the heat treatment that brings about washproof fixation of the swelling agent, 50 that during heat treatment they become concentrated on the surface as a result of evaporation and cause crosslinking of the cellulose at the surface of the fibers or threads in at least a slightly swollen state, whereas the interior is at most slightly swollen during crosslinking.

It has been found that the cellulosic materials disclosed in this application exhibit improved finishing effects with increased wet crease recovery and reduced losses in strength without impairment of the dry crease recovery by effecting the crosslinking of the cellulose in the presence of these organic agents which are (1) preferably of neutral reaction, (2) do not contain any hydroxyl groups and thus are not capable of chemical reaction either with the crosslinking agent or with the crosslinking catalyst used. These agents as previously mentioned exert a swelling action on the cellulose even in the absence of water, said agents preferably having a boiling point which is at most 50 C. below or at most 70 C. above the temperature employed in the crosslinking. The agents exhibit a swelling action on cellulose which corresponds to a yarn twist index determined in accordance with the test method described in Textile Research Journal, 32, pg. 1041 (December 1962), of at least 0.25, and in connection with which at most a small amount of water is present upon the crosslinking.

The use of these agents either alone or in conjunction with the other additives of this invention make possible an increase in soil repulsion.

The organic agents can be applied to the textile material either in pure form or in the form of an aqueous solution or emulsion, together with the crosslinking agent (and suitable, known crosslinking catalysts), or before or after the latter. They can be used in gaseous form before or during the crosslinking treatment. Those agents with relatively high boiling points have to be evaporated in a vessel with relatively simple seals. Since the boiling points of these operable swelling agents are higher than the normal curing temperature a very short contact must be effected to prevent premature curing (e.g. curing before the agents have had time to penetrate into the fibers or threads).

One embodiment of this method of the invention where the swelling agent is used alone in conjunction with finishing agent, which is preferred because of its simplicity and economy consists in applying the organic agents to gether with the crosslinking agent in the form of an aqueous solution or emulsion to the textile material, removing the water by drying and heating to effect the crosslinking. Drying and heating (curing) can be effected in one step by simply heating for a slightly longer time period.

Organic agents which have a yarn twist index of less than 0.25 do not exhibit the previously mentioned effects in accordance with the invention or do so to such a slight extent that their use is not worthwhile. Agents whose swelling action corresponds to a yarn twist index of at least 0.25 are suitable. The best results are obtained if the yarn twist index is equal to 1 or more. Agents which enter into a chemical reaction with the crosslinking agent or which make the crosslinking catalyst inactive by chemical reaction or buffering within the fiber or thread are less suitable. Good results are obtained for instance with substances of neutral reaction, such as for example, dimethyl sulfoxide; dimethyl fonnamide; dimethylsulfone; in which connection they can be used as mentioned in aqueous solution, i.e. strongly diluted with water, which makes the method very economical.

These swelling agents when used alone with crosslinking agent should have boiling points not less than about 50 C. below the crosslinking temperature of the cellulosic material. Also substances whose boiling points are higher than about C. above the crosslinking temperature can not be used.

The minimum curing temperature for the crosslinking agents used in the abrasion resistance process of this invention is approximately 130 C. If, however, stronger catalysts are used (for instance, free acids), the minimum curing temperature for most crosslinking agents can be reduced to well below C. As to the upper limit, very high temperatures are feasible if very short curing times are used. Generally speaking it is the yellowing of the fabric, and/or the thermal degradation of optical bleaching agents or dyestuffs which limits the curing temperature rather than the chemistry of the crosslinking system. However, about 200 'C. is the highest practical curing temperature to be used.

The amount of residual water present during the crosslinking stage of the process of this invention determines the balance between dry and wet creasing angles (i.e. dry and wet crease recovery). If it is high, wet creasing angles are high, dry creasing angles low. If there is as little as about 2% residual water or less present, then wet and dry creasing angles are high. If it is somewhere between, dry creasing angles also are somewhere in between. Thus the amount of residual water present during crosslinking should be maintained at or below about 20%, and preferably at about 10% or less of available water to the weight of the fabric. By available water is meant water which is not present in the form of hydrates, etc., and Fir/such, therefore, can cause swelling of the cellulosic ers.

The method of the invention is applicable to textile materials in the form of yarns or fabrics consisting wholly or partly of untreated or regenerated or modified cellulose. The new process is intended preferably and primarily for woven cellulosic textile fabrics but the advantages of the invention can also be obtained by treating knitted or non-woven fabrics. The preferred cellulose substance is cotton, which is preferably woven, for instance printed fabric, broadcloth and bed sheeting. Although the method is ordinarily applicable to fabrics formed entirely of cotton or rayon, the method is also applicable to fabrics containing synthetic fibers or filaments, for instance, ethylene glycol terephthalate polyesters, nylon and the polyacrylics. The cellulosic substance preferably forms at least about 30% by weight or more of the fabric to be treated, and rather about 60% or more.

Blends with other fibers as mentioned above can be used. For instance, spandex (or stretch) fibers such as Lycra, an expandable fiber produced by E. I du Pont de Nemours & Co., can be incorporated in blends with various cellulosic fibers. Conditions, of course, should be used which do not affect the properties of the non-cellulosic fiber component (e.g. curing temperatures which do not degrade spandex fibers).

The material may be in any state of finishing, but treatment should preferably be carried out, as with most ordinary crosslinking treatments, with resin reagents, aldehydes, etc., after desizing, bleaching, and insofar as colored goods are concerned, after dyeing.

The cellulosic fibers of this invention include natural, modified and regenerated cellulose, including cellulose which has been partially esterified or etherified in such a manner that there are crosslinkable hydroxyl groups remaining on the anhydroglucose units. For example, the lower hydrocarbon esters comprising the acetate, propionate, butyrate, benzoate, sulfate, phosphate and aryl and alkyl sulfate esters, the lower alkyl ethers comprising methyl and ethyl ether and the hydroxy alkyl ethers, including the hydroxy ethyl and carboxy methyl ethers, and the other known esters and ethers of cellulose can be used. The fabrics can be formed of natural cellulose substances, such as cotton, linen, jute or hemp, or synthetic cellulose substances, for instance, filamentary or staple viscose, unmodified or modified, e.g. rayon.

The finishing agents of this invention are capable of increasing the intermolecular cohesion or intermolecular bonding of the cellulosic fibers when utilized in accordance with the instant process to the point at which the cellulosic material becomes insoluble in cuprammonium. While there is no exact understanding of what actually takes place between and within the cellulosic fibers, and it is not intended that I be bound by any exact theory, it is felt that intermolecular cohesion is increased due to the introduction of new bonds. The exact nature of these bonds is not known definitively either. However, they are probably covalent although hydrogen bonding and noncovalent bonding may also be at least in part responsible for the increasing intermolecular cohesion. A certain amount of intramolecular bridge formation may also take place. In particular the increased intermolecular cohesion is probably created by forming bridges between cellulosic macromolecules. The bridge-building may consist in covalent crosslinking or in the formation of complexes, hydrogen bridges, or other intermolecular linkages.

The following are typical of the croslinking agents that give primarily covalent bonds:

So-called thermosetting synthetic resins of the reactant type (in the form of their precondensates or components), obtainable from nitrogen compounds with an amide type nitrogen grouping (--CONH) and monoor polyfunctional carbonyl compounds, especially aldehydes (e.g. reaction products of formaldehyde, glyoxal, acrolein with urea, or homologs thereof, in particular cyclic alkylene ureas, ureines, so-called triazones, or other heterocyclics with the grouping NHCO NH; monomeric or polymeric crosslinking agents with aldehyde groups in particular low-molecular aldehydes (formaldehyde, glyoxal, acrolein, acetaldehyde, used as such or in the form of derivatives such as acetals, enol ethers, diglycidyl ethers, glycerols, polymers or other reaction products which, under the conditions employed, are capable of crosslinking cellulose or splitting oif aldehyde with crosslinking properties), dior polyfunctional crosslinking agents containing epoxides, diepoxides, isocyanates, vinylsulfo compounds such as divinyl sulfone and divinyl sulfoxide or other reactive vinyl or acyl groups, crosslinking organic halogen compounds such as epichlorohydrin, di-chlor0-1,3 propanol, dichloro-2,3-propanol and mixtures there of related halogen hydrins, dihalohydrins and dicarboxylic acids in free form in the form of derivatives, dior polyfunctional onium compounds (sulfonium, phosphonium, etc.), cellulose-crosslinking reaction products of two carbonyl compounds, for example, ketones with low-molecular aldehydes (especially formaldehyde, acrolein, glyoxal). All the abovementioned compounds are, of course, brought to reaction in the usual manner by means of suitable catalysts including acid, basic, potentially acid or basic substances, free radicals and radiation. This reaction may take place in the presence of agents that have a swelling effect on the fiber material as previously mentioned and/ or known products that control the friction between fiber or yarn components or other known additives such as dyes or dyeforming agents, white or colored pigments, and finishes.

It is also possible to use crosslinkages obtained in situ by means of physical or physicochemical effects, e.g. heat treatments, exposure to high-energy radiation such as corpuscular radiation, very high frequency radiation, substitution reactions or grafting polymerization reactions with the cellulose hydroxyl groups, and the intercalation or creation of high polymers.

In general an agent will be suitable if, While improving the intermolecular cohesion of the cellulose, it increases its elasticity and reduces its stretchability.

Apart from the finishing agent, the bath usually contains catalysts to catalyze the bridge-building, whether by acid or alkaline reaction or the splitting off of radicals, etc.

In addition, softeners, white, colored or dye-forming pigments, surfactants, brightening agents, water-repelling agents, and finishes may be included. It is possible to employ solutions, emulsions, or dispersions or foam-type finishing baths, as well as multi-phase systems containing solvents with different boiling points and/ or different dissolving capacity for one or several of the components present in the bath.

If desired and when feasible, the finishing agent can be applied to the textile material in gaseous form. This also applies to the catalyst. Moreover, the application process may consist of several stages.

Aldehydes of low molecular weight such as formaldehyde, glyoxal, acrolein and their homologues are examples of crosslinking agents which may be used in the gaseous state. Other gaseous compounds in particular vinylic or acrylic have been deposited within or grated on cellulose fibers and threads successfully.

After the finishing agents and suitable catalysts, and where necessary other members of the above-mentioned group of agents, have been applied, and the ratio of the concentration of hydroxyl groups to the concentration of finishing agents and/or the effective catalyst concentration at the surface of the fibers or threads has been varied, before or after evaporation of the liquid phase, in the manner described, the increase in intermolecular cohesion and wash-proof fixation of the finishing agent are induced, preferably by heat treatment (if desirable, only after performing other known finishing or processing operations Such as, for example, mechanical deformation, garmentmaking treatments, etc.). Where necessary, the cellulose may also be in at least a slightly swollen state. Finally, if so desired, the material can be washed, given a final finish, and mechanically or chemically shrunk; yarn can be woven and cloth cut.

The treatment proposed can also be applied to methods in which after the application of the finishing agent, but before washproof fixation of the latter, the textile material is mechanically deformed. It can also be used if cloth is worked into articles of clothing after the application of the finishing agent, but before its washproof fixation, and only subsequently subjected to a treatment designed to increase the intermolecular cohesion of the cellulosic threads.

The instant process thus can be used in what is known as permanent press. In this process generally the fabric is impregnated at the mill or finishing plant in the piece with an appropriate crosslinking agent or mixtures of different crosslinking agents and suitable catalysts. It is then usually dried under mild conditions so as not to cure or set the crosslinking agent. That is, the chemical system has either not been catalyzed or heated sufficiently and only partial or no crosslinking or joining has yet taken place between the molecules of the fibers and those of the crosslinking agent. These partially treated fabrics are then cut, sewn and pressed into garments like any other fabrics. The final pressing operation or a heat treatment in an oven may then provide the curing or heating step.

It is also now possible to cure the fabric with crosslinking agent and later, at any time, reverse this process with suitable treatment. At a later time the fabric then can be treated elfectively in accordance with this invention.

Permanent press: There are many methods of achieving this desired result. Three of the more common approaches which can be utilized are (a) In case of oven cure the finisher puts on the crosslinking agent plus catalyst, and inactivates the catalyst during or after drying without curing (i.e., without heating to higher temperatures). Gaseous and liquid inactivation systems are applicable. In the case of precure systems the same applies, but the crosslinking agent would be partially cured, or only one component of the crosslinking system would be cured according to the process of this invention. (b) The finisher puts on the crosslinking agent, dries, but does not cure. After make-up operations the garment is treated with gaseous catalyst deactivators before it is cured in an oven. The same procedure is used as (b), but the gaseous deactivator is present in the Curing oven itself.

The following representative examples illustrate the process and products of this invention. Percentage compositions are by weight throughout the entire specification unless otherwise noted.

EXAMPLE I A cotton fabric (poplin, yarn number Ne 40/40, thread count 53/25 per cm.), that had been desized, boiled, bleached and mercerized, was treated with 200 grams per liter of dimethylol-(N-ethyl) -triazone Permafresh SW, a finishing agent capable of crosslinking cotton (made by Sun Chemical Corporation, Warwick Chemical Division, Wood River Junction, R.I.), 30 grams per liter Primal HA 8 (crosslinkable acrylic polymerizate, made by Rohm and Haas, Philadelphia, Pa.), and 50 grams per liter Permafresh catalyst SWC (a potentially acid metal salt catalyst made by Sun Chemical Corporation, Warwick Chemical Division, Wood River Junction, R.I., together with 30 grams per liter polyethylene softener, Mykon Lubricant WM (made by Sun Chemical Corporation, Warwick Chemical Division, Wood River Junction, R.I.), whereupon, in a first experiment, the fabric was dried in the usual way. Then one piece (specimen 1) was treated for one minute with ammonia gas before crosslinking (the ammonia serves to deactivate the catalyst at the surface), whereupon crosslinking was induced by heating at 150 C. for minutes. Another piece (control) was subjected to the same heat treatment without having been treated with ammonia.

Another piece (specimen 2) was treated with ammonia gas for five minutes while it still had a residual moisture content of 25%. Then it was likewise treated for five minutes at 150 C.

A third piece (specimen 3) was treated for ten minutes with ammonia gas before drying, i.e., still in the wet state, and then again condensed for five minutes at 150 C.

After condensation, i.e., before evaluation, all the specimens were washed at 80 C.

1 AATCC standard B 88-19601. 2 ASTM D 1175-55 T.

Thus, the pieces treated in accordance with the invention had much better wear resistance and tear strength than the control. The crease angles were only slightly lower, the wash-and-wear effects the same.

EXAMPLE II A cotton fabric (cambric, thread count 39/35 per cm., yarn number Ne B 60/50) was given the same preliminary treatment as in Example I, then finished with the same formula and dried. Then it was treated with a solution of 20 parts octadecylamine (commercial quality) in parts isoamyl alcohol (ctodecylamine, whose molecular structure counteracts any tendency to diffuse into the fibers, is an agent for reducing the effective catalyst concentration at the surface, isoamyl alcohol is a relatively high-boiling hydroxyl compound which, at least in the early stage of condensation, brings about an increase in the number of hydroxy groups capable of forming bridges with the crosslinking agent), this being followed by condensation for 4 minutes at C.

A control specimen was condensed in the same way after drying, without being treated with octadecylamine. After condensation, both pieces were washed with 2 grams per liter of non-ionic washing agent at 80 C.

Wear resistance 1 (Accelerotor) loss of weight after Crease treatment for 3 min.

angle at 3,000 rpm.

Results (degrees) (percent) Control specimen... 265 24 Treated specimen 255 12. 5

1 Testing Method T 93-1959, Year Book of the American Association of Textile Chemists and Colorists, pg. B93 (1964).

EXAMPLE III EXAMPLE IV In a further experiment, employing the same treatment as described in Example II, dimethylsulfoxide was used for the long-chain aliphatic amine. The crosslinking agent and catalyst were applied in aqueous solution, whereupon the fabric was dried. The fabric was then treated with the 20% solution of octadecylamine in dimethylsulfoxide and heated for 3 minutes at C. to induce crosslinking. The dimethylsulfoxide, which has a strong swelling action on cellulose, becomes concentrated at the surface of the fibers or threads as a result of partial evaporation, so that the outer regions of the fibers and threads are crosslinked in a more swollen state than the inner regions, which leads to an additional improvement in the mechanical properties.

The wear resistance (Accelerotor) of fabric so treated was twice that (wear after 3 min. at 3000 r.p.m.l0.5%) for a similarly finished and condensed specimen that had not been treated with dimethylsulfoxide and octadecyl- EXAMPLE V The fabric mentioned in Example I was finished, as therein described, with a crosslinking agent, a crosslinking catalyst, and the corresponding additives and dried to a residual moisture content of 25% Then it was treated with a strongly thixotropic, thickened 2% solution of soda ash in water (thickener: Meyprogum AC 7, a product made from locust bean cflour and galacto-mannane, made 'by Meyhall Chemical AG, Sonnenweisenstrasse, Kreuzlingen, concentration 60 grams per liter), and immediately dried. Finally, it was again condensed for minutes at 150 C. and washed.

The crease angle was 2407, the wash-and-wear effect 4, the wear resistance 250.

EXAMPLE VI A cotton fabric (poplin, yarn number Ne 40/40, thread count 53/25 per cm.), which had been steeped, boiled, bleached, and mercerized, was finished with 100 grams per liter of dimethylol-(N-ethyl)-triazone (Permafresh SW, produced by the Sun Chemical Corporation, Warwick Chemical Division, Wood River Junction, R.I.,) 50' grams per liter of Permafresh Catalyst SWC (potentially acid metal salt catalyst, produced by the Sun Chemical Corporation, Warwick Chemical Division, Wood River Junc tion, R.I.), and 30 grams per liter of a polyethylene softener, whereupon the material was treated with ammonia gas as the anticatalyst in a variety of manners.

Sample 1 was dried and treated in dry atmosphere with the quantities of ammonia, set forth in the following table, during heating at 150 C. for 4 minutes to increase the intermolecular cohesion of the celloluse by crosslinkage.

Sample 2 was treated the same way, but after drying the sample was conditioned at 20 C. and 65% relative humidity and crosslinked in this state in the presence of ammonia gas as set forth in the table.

Sample 3 was dried only partially after finishing (residual moisture 30%), then crosslinked in the presence of ammonia gas as set forth in the table.

Sample 4 was crosslinked after drying in the presence of ammonia gas as set forth in the table, there being in the gas volume 1 gram of water per liter of air.

Sample 5 was dried after finishing in the presence of ammonia gas, then crosslinked as described.

Sample 6 was treated with ammonia gas immediately before the crosslinking, the ammonia gas being removed practically completely from the fabric before the heat treatment by means of blowing air. The contact time of the textile material with the ammonia was 1 minute.

A reference sample was finished and dried and crosslinked in exactly the same manner, but without the addition or action of NH on the fabric.

The wear resistance of the specimens, and that of a specimen treated with exactly the same formula and similarly condensed, but not exposed to the surface action of an anticatalyst in accordance with the invention, was determined from the loss of weight after 3 minutes in the Accelerotor (3000 r.p.m.).

All samples were washed before evaluation.

Crease angle Abrasion NH cone. strength im- Sample (ce./l. air) Wet Dry provement 1a 0. 5 285 270 6 b 1 280 270 4 c- 5 285 280 28 2a 0. 5 275 260 32 b- 1 260 270 49 c 5 275 250 3a 0. 5 235 230 92 b 1 225 235 96 c 5 220 225 97 4a. 0. 5 285 265 59 b- 1 285 265 59 e 5 285 255 42 5a 0. 5 240 240 83 b 1 245 245 83 c. 5 270 265 73 6a- 0. 5 275 265 48 c 5 280 280 40 Reference sample 280 270 0 1 Percentage reduction of the abrasion in the Accelerotor (3 min, 3,000 r.p.m.) The reference sample (with the action of NHB) shows an abrasion of 9.5%. An abrasion of for instance 2.9% (samplefic) thus corresponds to an improvement of 73% compared with the reference sample.

EXAMPLE VII A reinforced cotton (pretreated like the fabric in EX- ample VI) was, after finishing with 80 grams per liter of dimethylol-propylene urea, 14 grams per liter of Zinc nitrate, and 30 grams per liter of polyethylene softener, subjected to a treatment with various reagents, which brought about a surface neutralization or buffering of the catalyst used, and hence increased abrasion resistance. Treatment was conducted under varying conditions, either immediately after the finishing, i.e. in the wet state, with a gaseous medium (ammonia) capable of inactivating the catalyst, or after the drying, while drying and during the fixation of the finishing agent. In other cases the use of the reagents occurred after the drying out or evaporating -C., to bring about a crosslinking of the cotton (to insolubility in copper oxide ammonia). The abrasion strength of the samples, as well as that of a fabric section treated with exactly the same formula and condensed in the same manner but not treated superficially with an anticatalyst according to the invention, was determined by measuring the weight loss caued by a treatment for 3 minutes (speed 3000 r.p.m.) in the Accelerotor. In addition, the crease angle was determined as a measure of the conversion effect brought about by the increase of the intermolecular cohesion.

Reduction Ooncen abra- Crease tratlon Contact sion angle Sample Number Reagents used (percent) Method time (percent) (degrees) 1- Polyvinyl pyrrolidone 10 Solution in i-amyl r. 60 245 alcohol. 5 In water- 40 260 5 -do 85 200 5 In i-amyl alcohol 260 10 do 230 205 40 260 25 265 35 255 35 255 40 255 31 265 l 5/g./100 1. air. 2 20/g./100 1. air.

1 EXAMPLE VIII A section of the fabric mentioned in Example VI was finished with the formula stated therein, but 5 grams per liter of ammonium carbonate was present in the bath. The ammonium carbonate decomposed during the subsequent drying and crosslinking (at 150 C. for 4 minutes) with separation of ammonia gas. This brought about a surface buffering of the potentially acid catalyst used. At slightly reduced crease angle (260 as compared with 280 without ammonium carbonate) the abrasion strength (Accelerotor) was 40% higher than in the control sample. The wash-and-wear effect, as determined and described for Example XVI in both samples, was 4-5.

EXAMPLE IX A cotton shirt material was finished, after the usual pretreatment (steeping, boiling, bleaching and mercerizing), with 90 grams per liter of dimethylol carbamate (reactant resin), 14 grams per liter of a potentially acid metal salt catalyst, and 30 grams per liter of polyethylene softener (30% solids content), then dried and immediately before crosslinking passed at a speed of 100 meters per minute through a chamber in which a concentration of 0.4% of ammonia gas (based on volume of air present) was maintained. The contact time was 5 seconds. The fabric web ran from this chamber directly into the crosslinking furnace, in which the crosslinking was brought about at 155 C. This was followed by washing and evaluation.

Ammonia With Without Tensile strength:

arp, kg 56 48 35 29 Tearing strength (Ehnendor 950 780 Weft 800 600 Wash and Wear effect 4 4 Flex abrasion strength (Stoll apparatus) Weft 1, 800 800 Crease angle 245 255 EXAMPLE X EXAMPLE XI A cotton fabric (percale) was, after the usual pretreatment (steeping, boiling, bleaching, mercerizing), finished with 160 grams per liter of commercial Formalin (formaldehyde content 36%), 16 grams per liter of zinc nitrate, and 30 grams per liter of polyethylene softener, and dried at 90 C. In sample 1 the drying took place in the presence of 0.05% of ammonia gas (based on the volume of air present), whereupon the crosslinkage was brought about by heating to 150 C. for 4 minutes. In sample 2 0.1% of ammonia gas was present during drying. In sample 3 0.05 of ammonia gas was present during drying, the fabric showing in this latter sample a residual m i ture of 5% before the crosslinking.

Before evaluation, all sections were thoroughly washed (60 C., 2 grams per liter of non-ionogenic detergent) and then evaluated:

Abrasion Crease strength angle improvement 1 (degrees) (percent) S ample 1 265 2 295 20 3 250 50 Reference sample (without ammonia) 300 1 The abrasion of the reference sample in the Aecelerotor was 19%.

EXAMPLE XII A section of the poplin mentioned in Example VI was finished with grams per liter of a 50% solution of dimethylol dioxylethylene urea, 12 grams per liter of magnesium chloride, and 30 grams per liter of polyethylene softener and then dried (100 C.). Then a crease was produced in a small section (20 x 20 cm.) by ironing with an iron at 100 C. (i.e. without creating crosslinkage at the points of contact with the iron). The creased or folded section was then heated in a drying cabinet (air circulation) for 4 minutes at 150 C. The atmosphere contained some ammonia gas besides air, causing a surface inactivation of the catalyst.

The abrasion strength at the ironed-in crease, fixed washfast by crosslinkage (determined by abrasion to hole formation), was 35% better than in a sample treated in similar manner but heated in air without the admixture of ammonia.

In a second test the ammonia treatment was conducted after the drying, followed by ironing-in of the crease at 100 C. Then crosslinking was effected as described above. The improvement of the abrasion strength was about 40%.

EXAMPLE XIII Cotton yarn (Ne 40/ 1, carded) was, after bleaching (sodium chlorite) and mercerizing, finished in skein form with 90 grams per liter of the triazone reactant resin mentioned in Example VI, 50 grams per liter of the catalyst mentioned in Example VI, and 40 grams per liter of a crosslinkable polyacrylic ester. By centrifuging the bath absorption was reduced to 80% of the weight of the material. The yarn was then dried, conditioned (moisture content of the material 56%) and treated in the presence of 0.05 of ammonia gas (based on the volume of air present) in a heating chamber for 10 minutes at C., during which time crosslinking of the cotton occurred.

On testing the abrasion strength on a yarn abrasion apparatus, an improvement of 30 to 35% was found compared with a reference sample crosslinked in a similar manner but in the absence of ammonia.

EXAMPLE XIV Poplin, finished with crosslinking agent, catalyst and softener in accordance with Example I, was dried (100 C.). A crease was then ironed in a small piece (20 x 20 cm.) by ironing with an iron heated to 100 C. (i.e., without inducing crosslinking at the points of contact with the iron). The creased fabric was then heated in a drying oven (circulating air) for 4 minutes at C., the atmosphere containing some ammonia gas as well as air. The ammonia served to deactivate the catalyst at the surface.

The wear resistance at the crease, made was'hproof by crosslinking, as determined by an edge abrasion apparatus, was more than 20% better than that for a specimen similarly treated but heated in air without an admixture of ammonia.

EXAMPLE XV A cretonne made of regeneratedcellulose fibers (rayon staple) was finished with 200 grams per liter melamineformaldehyde prccondensate, 16 grams per liter zinc nitrate, and 20 grams per liter of an anion-active softener, dried, treated with air containing ammonia gas for 20 seconds, and then heated for 4 minutes at 140 C., to bring about washproof fixation of the melamine-formaldehyde precondensate and improvement of the intermolecular cohesion of the regenerated cellulose (after treatment it was insolube in cuprammonium and crease recovery.

The wear resistance of the piece thus treated was 30% better than that of a specimen finished in the same way, but heated without the addition of amonnia (Accelerotor).

EXAMPLE XVI A cotton fabric (poplin) after desizing, bleaching, and mercerizing was finished with 200 grams per liter of Permafresh SW, 50 grams per liter of a potentially acid metal-salt catalyst identified as Permafresh SWC, produced by the Warwick Chemical Co., and 40 grams per liter of an acrylic polymer, there being admixed to the bath in Test 9a 33 grams per liter of diethyl formamide (Yarn Twist Index less than 0.1), in Test 912 33 grams per liter dimethyl formamide (Yarn Twist Index 0.25 to 0.35) and in Test 90 33 grams per liter of dimethyl sulfoxide (Yarn Twist Index more than 1) while in Test 9d no addition was added (comparison test). The finishing was carried out by padding the fabric in an aqueous solution containing all the agents mentioned, then squeezed between the rollers of the padding mangle to reduce the pickup to about 70% of the weight of the fabric. After the finishing, drying was affected in all cases under identical conditions, followed by heating for 3 minutes at 150 C. to produce the crosslinking. The evaluation of the samples gave the following results:

Resistance Wash Crease angle 2 to abrasion,

and (degrees) loss in the Improvement wear Accelerotor 3 over 9d Test effect 1 Dry Wet (percent) (percent) 9a 4 280 260 13. 5 11 9b 4-5 285 270 11. +11 90 4-5 285 280 8. 0 +34 9d 4 280 255 12. 2

abrasion,

EXAMPLE XVII A fine cotton fabric (percale) after the customary preliminary treatment (same as in Example IX) was treated with the formula indicated in Example I, in addition of 75 grams per liter of dimethyl sulfoxide being made to the bath in Test 10a, while Test 1012 (no addition) served as comparsion.

Tear strength Crease angle in filling (degrees) direction Test (Weft) (kg.) Dry Wet WW-efiect 10a i 11. 260 275 4 b 9. 5 255 255 3 EXAMPLE XVIII The cotton poplin mentioned in Example XVII was finished with 120 grams per liter dimenthylol ethylene urea and 14 grams per liter zinc nitrate, 100 grams per liter of dimenthylsulfoxide being added in Test No. 11a but not in Test No. 11b (comparison).

Loss in re- Tear Crease angle sistanee to strength (degrees) abrasion loss (AcceL) Test (percent) Dry Wet (percent) WW-efiect;

18 EXAMPLE XllX A spun rayon fabric, which had been desized and bleached, was finished with 250 grams per liter of dimethylolethylene urea and 20 grams per liter of zinc nitrate, 75 grams per liter of dimethylsulfoxide being added in Test 12a but not in Test. 12b.

To a cotton print cloth (desized, bleached, mercerized) a formulation in accord with that given in Example 1 was applied by padding (pick-up 75%). The fabric then was dried to less than 3% humidity at 100 C., and passed through a bath containing 1.5 g. per liter soda ash (as anticatalyst) at room temperature, speed 30 meters per minute, squeezed once to reduce the pick-up to 30-35% and immediately dried at 100 C. The concentration of the soda ash was kept constant, the time of contact (between first contact and squeezing) with the soda ash solution was kept very short (about 1 second). After drying the fabric was cured at 150 C. during 4 minutes.

A control was treated identically, but without soda ash treatment.

Creasing Abrasion Wash angle, resistance and dry improvement wear (percent) (Accelerotor) rating (percent) Beginning of run 275 50 4. 5 Middle of run.. a 280 43 4. 5 End of run 280 45 4. 5 Control 290 4. 5

The concentrations of the crosslinking agents should be applied in the range of from about 1% to 20% by weight of crosslinking agent to the weight of the cloth. This means crosslinking agent fixed on fabric as distinguished from crosslinking agent applied to fabric. There are, of course, widely differing conditions, formaldehyde, for instance, is applied to fabrics in concentrations of grams to 250 grams formaline per liter, i.e., 30 grams to 80 grams formaldehyde per liter, of which only about 5% or less of the weight of the formaldehyde is actually bonded to cellulose, i.e., cannot be rinsed off.

Crosslinking catalysts are used in concentrations varying with the catalyst and the crosslinking agent, but generally speaking the crosslinking agent/catalyst ratio by weight should be between 100:1 and 1:1, the vast majority being present in amounts of between 20:1 and 5:1.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is understood that this invention is not to be limited except as defined in the appended claims.

What is claimed is:

1. A process for treating cellulosic fibers to obtain a greater degree of cross-linking in the core of said fibers than at the surface periphery thereof substantially continuously throughout the length of said fibers which comprises impregnating said fibers with from about 1 to about 19 20 percent, by weight of fibers, of a finishing agent capable of cross-linking cellulosic hydroxyl groups to render said cellulosic fibers insoluble in cuproammonium and a catalytic amount of a catalyst capable of promoting the cross-linking reaction of said finishing agent, adjusting the moisture content of said fibers so as to contain not more than about 30 percent, by weight, of moisture, subjecting said fibers to an atmosphere containing from about to about 4000 millimoles per cubic meter of an agent in a gaseous state which interferes with cross-linking, the concentration of said agent in said atmosphere, the duration of exposure of said fibers to said atmosphere, the relative humidity of said atmosphere, and the moisture content of said cellulose fibers being such as to cause said agent to inhibit substantially cross-linking essentially at the sun face periphery of said cellulosic fibers substantially continuously along the length of said fibers, and subjecting said fibers to conditions causing cross-linking of said cellulosic hydroxyl groups by said finishing agent.

2. The process according to claim 1 in which said agent which interferes with cross-linking comprises gaseous ammonia.

3. The process according to claim 1 in which said fibers are present in a fabric.

4. The process according to claim 1 in which said finishing agent is applied to said cellulosic fibers in the form of an aqueous solution.

5. The process according to claim 1 where said moisture content of said cellulosic fibers is not more than 20 percent by weight of said fibers.

6. The process according to claim 1 wherein said moisture content of said atmosphere of the agent which interferes with cross-linking is not more than 15 g. water per cubic meter at 20 C.

7. The process according to claim 2 wherein the gaseous ammonia is present in said atmosphere in an amount of from about 011 to about 10 grams per cubic meter.

References Cited UNITED STATES PATENTS NORMAN G. TORCHIN, Primary Examiner J. E. CALLAGHAN, Assistant Examiner U.S. C1.X.R. 

